// 多个选择器集成扩展
p:extend(.style, .img) {

    font-size: 20px;
}

.style {
    background: green;
}

.img {
    font-size: 25px;
}

//多级继承

.thirdClass {
    color: #888;
    &:extend(.secondClass);
}

.secondClass {
    color: #777;
    &:extend(.firstClass);
}

.firstClass {
    color: #666;
}

//嵌套继承

.bucket {
    font-weight: 400;

    tr & {
        // nested ruleset with target selector
        color: blue;

    }
}

p:extend(tr .bucket) {}

//精确匹配

*.class {
    color: blue;
}

.noStar:extend(*.class) {}

link:hover:visited {
    color: blue;
}

.selector:extend(link:hover:visited) {}

//media

@media print {
    .screenClass:extend(.selector) {}
}

.selector {
    // ruleset on top of style sheet - extend ignores it
    color: red;
}

@media screen {
    .selector {
        // ruleset inside another media - extend ignores it
        color: blue;
    }
}

.class1{
    color:red;
}
.class2{
    &:extend(.class1);
}
.class3:extend(.class2){

};